National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KMFR 231013
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
313 AM PDT THU MAY 23 2013

.DISCUSSION...CURRENT WATER VAPOR IMAGE SHOWS THE UPPER LOW SPINNING
NEAR THE OREGON/WASHINGTON BORDER AND THIS IS EXPECTED TO CONTINUE
THROUGH FRIDAY MORNING BEFORE WEAKENING AND LIFTING NORTHEAST INTO
WASHINGTON STATE FRIDAY AFTERNOON. A WEAK UPPER TROF REMAINS OVER
THE FORECAST AREA FRIDAY NIGHT THROUGH SATURDAY.

PRECIPITATION HAS DECREASED AND ENDED DURING THE OVERNIGHT HOURS.
HOWEVER EXPECT SHOWERS TO INCREASE AGAIN LATE WITH A SERIES OF
SHORTWAVES ROTATING AROUND THE UPPER LOW. MOST OF THE SHOWERS SHOULD
BE CONCENTRATED ALONG AND WEST OF THE CASCADES AND NORTHERN KLAMATH
AND LAKE COUNTIES AND MORE ISOLATED IN NORTHERN CAL. THERE MAY BE
ENOUGH INSTABILITY FOR ISOLATED THUNDERSTORMS EAST OF THE CASCADES
IN THE AFTERNOON...BUT THIS WILL BE THE EXCEPTION. MOST HOURS AND
LOCATIONS WILL HAVE JUST INSTABILITY SHOWERS.

ANOTHER SHORTWAVE ROTATING AROUND THE UPPER LOW IS EXPECTED TO MOVE
INTO THE NORTHWEST PART OF THE FORECAST AREA TONIGHT RESULTING IN A
CONTINUATION OF SHOWERS MAINLY NORTH OF THE UMPQUA DIVIDE AND
CASCADES NEAR AND NORTH OF CRATER LAKE. ELSEWHERE SHOWERS ARE
EXPECTED TO BE MORE ISOLATED. PLENTY OF CLOUD COVER REMAINS OVER THE
AREA WHICH WILL LIMIT THE AMOUNT OF COOLING AT NIGHT. NOT AS
CONFIDENT WE`LL GET A SUSTAINED PERIOD OF FREEZING TEMPERATURES IN
THE KLAMATH BASIN AND SHASTA VALLEY.

THE UPPER LOW WILL MOVE NORTHEAST INTO WASHINGTON STATE FRIDAY AND
AS IT DOES SHOWERS WILL DECREASE FROM SOUTH TO NORTH WITH MOST
EXITING THE FORECAST AREA BY FRIDAY EVENING. WE`LL CATCH A BREAK IN
SHOWER ACTIVITY FRIDAY NIGHT.

ANOTHER...BUT WEAKER UPPER TROF SWINGS INTO THE AREA SATURDAY
MORNING WITH SHOWERS EXPECTED TO INCREASE WEST OF THE CASCADES. THE
NAM SHOWS QPF BREAKING OUT EAST OF THE CASCADES IN THE AFTERNOON
WHICH IS MOST LIKELY A RESULT OF INCREASING INSTABILITY AND WEAK
SHORTWAVES PASSING BY.

WEAK TROFING REMAINS OVER THE AREA SUNDAY. HOWEVER THE GFS SUGGEST
THE TROF AXIS WILL MOVE EAST IN THE AFTERNOON WITH WEAK RIDGING
BUILDING FROM THE WEST. CONFIDENCE IS NOT HIGH ON THE GFS SOLUTION
THEREFORE WE`LL KEEP THE CHANCE OF SHOWERS IN THROUGHOUT THE DAY.
-PETRUCELLI


&&

.AVIATION...

BASED ON THE 23/06Z TAF CYCLE.

A PERSISTENT STREAM OF MOISTURE WILL CONTINUE TO MOVE INTO THE NORTH
COAST, UMPQUA, AND NORTH CASCADES THIS MORNING. THIS WILL KEEP
LIGHT RAIN GOING ALONG THE COAST WITH SCATTERED TO NUMEROUS
SHOWERS INLAND TO THE CASCADES WITH MVFR CIGS AND OCCASIONAL MVFR
VIS OVER THIS AREA. MOUNTAIN OBSCURATION WILL ALSO BE FAIRLY
WIDESPREAD ON THE WEST SIDE. SHOWERS WITH MVFR CIGS ARE ALSO
ONGOING IN THE KLAMATH BASIN, BUT THESE SHOWERS WILL DECREASE
AROUND DAYBREAK. SHOWERS ARE MUCH MORE ISOLATED WITH GENERAL VFR
CONDITIONS ELSEWHERE ON THE EAST SIDE AND CALIFORNIA. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FREEZE WARNING UNTIL 9 AM PDT THIS MORNING FOR ORZ029.

CA...FREEZE WARNING UNTIL 9 AM PDT THIS MORNING FOR CAZ084.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
     UNTIL 11 PM PDT THIS EVENING FOR PZZ350.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT THIS
     MORNING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ370-376.

$$